After graduating as the valedictorian from Brookline High School (Brookline, Massachusetts), O’Brien entered Harvard University. Throughout his college career, he was a writer for the Harvard Lampoon humor magazine. During his sophomore and junior years, O’Brien served as the Lampoon's president, making him only the second person ever to serve as president twice, and the first person to have done it in 85 years. He graduated magna cum laude from Harvard in 1985 with a concentration in History and Literature.

Television career O’Brien moved to Los Angeles upon graduating from Harvard to join the writing staff of HBO's Not Necessarily the News. He spent two years with that show, and performed regularly with improvisational groups like The Groundlings. He also acted in corporate infomercials to earn money during this period.

After Not Necessarily the News, O’Brien worked as the warm-up comic for The Wilton North Report, a Fox show that was on the air for just four weeks.

In January 1988 Saturday Night Live's executive producer Lorne Michaels hired O’Brien as a writer. During his 3½ years on SNL he wrote such recurring sketches as "Mr. Short-Term Memory" and "The Girl Watchers", the latter of which was first performed by Tom Hanks and Jon Lovitz. O’Brien also wrote the sketch "Nude Beach", which became infamous due to the fact that the word penis appeared in it no fewer than 42 times, much of it in the form of song . He also appeared as an extra in some skits, occasionally with a speaking role. In 1989, he and the other SNL writers were awarded an Emmy Award for Outstanding Writing in a Comedy or Variety Series.

While on a writers' strike from Saturday Night Live following the 1987-1988 season, Conan put on an improvisational comedy revue in Chicago with fellow SNL writers Bob Odenkirk and Robert Smigel called Happy Happy Good Show.

In the spring of 1991, O’Brien left SNL to write and produce a pilot for the television show Lookwell, starring Adam West. It was broadcast on NBC in July but was not picked up as a series. That fall, O’Brien signed on as a writer and producer for the Fox series The Simpsons, where he also became a supervising producer. In a speech he gave at Harvard on Class Day in 2000, O’Brien credited The Simpsons with "saving" him, a reference to the career slump he was experiencing prior to his hiring for that show . During his time as a writer for The Simpsons, he created the character of Captain Horatio McCallister (the Sea Captain) and he named Patty and Selma Bouvier's iguana Jub-Jub (something Conan would say during awkward silences while writing). Of the episodes he wrote while there, he considers "Marge vs. the Monorail" to be his favorite.

Late Night On April 26, 1993, Lorne Michaels chose O’Brien to be David Letterman's successor as host of Late Night and Andy Richter signed on as his sidekick. Initially O'Brien was only signed on as a writer and producer for the new show, but when no host was found during the auditions, the hosting duties were given to him. It received generally unfavorable critical reviews for the first 2-3 years after its debut. Indeed, the show was reportedly cancelled by network executives, but was allowed to remain on a week-to-week basis when it was realized there was no programming available to replace it.

Since then, however, O’Brien and the Late Night writing team have consistently been nominated for an Emmy Award for Best Writing in a Comedy or Variety Series, though they have not won as of 2006. In 1997, 2000, 2002, 2003, and 2004 he and the Late Night writing staff won the Writers Guild Award for Best Writing in a Comedy/Variety Series.

In 2001 he formed his own television production company, Conaco, which has subsequently shared in the production credits for Late Night.

In the 2003-04 television season, Late Night with Conan O’Brien averaged 2.5 million viewers each week, easily beating every other show in its time slot.

Other work In 2005, O'Brien appeared in The White Stripes' music video, "The Denial Twist". The band had previously been a week-long musical guest on Late Night when they were promoting their 2003 album, Elephant. He has appeared on the equally surreal (and late) talk show Space Ghost Coast to Coast, Episode 77: Fire Ant, in which he and Space Ghost argue between themselves about a number of things, including whether or not anyone actually watches SGC2C. Space Ghost later quips "Well that's very stupid, and you won't make it in television," an obvious parody of early reviews of O'Brien's show. After a while, Space Ghost ignores the interview entirely to follow a fire ant that bit him (for about 11 straight minutes). As Space Ghost is crawling out of the studio, O'Brien gripes that "For all these people know, my show is...a...cop...show...on Fox...or something," to which Space Ghost replies "...Isn't it?"

On March 7, 2006, NBC announced that it had ordered a pilot episode for Andy Barker P.I., a new comedy executively produced by O'Brien (who will also co-write the pilot). The show will star O'Brien's former sidekick Andy Richter.

On September 27, 2004, NBC announced the planned 2009 retirement of Tonight Show host Jay Leno. O’Brien was named Leno's successor .

Partial filmography The Office - 2006 Robot Chicken - 2005 Andy Richter Controls the Universe - 2003 Storytelling - 2001 Saturday Night Live - 1991, 2001 Spin City - 1998 The Single Guy - 1996 Arli$$ - 1996 Mr. Show with Bob and David - 1995